Traditionally, rendering SAR images requires, at the very least, big memory storage when a SAR renderer is used to generate all variety of target images. The severe hardware requirements necessitate processing to be performed off-line or not in real time. Predicting SAR images from CAD models is a very complex problem that cannot be addressed correctly by applying rendering techniques developed for simulation of optical images. Specialized software packages available in the industry for performing this processing, like Xpatch by Leidos, Inc., are very complex to learn and take significant time to run. In addition, they require high fidelity CAD models with accurate settings of electromagnetic properties of all parts of the CAD models being utilized, further exacerbating the already demanding hardware requirements.
To enhance understanding of the disclosure herein, various basic principles of SAR are presented. FIG. 1 shows the SAR viewing geometry and the relations between slant samples 102i, 102ii on a slant plane 102 and ground samples 104i, 104ii on a ground plane 104. The sample spacing on the slant and ground planes are related via a function of the SAR's grazing angle iv, which is defined as the angle between the radar line of sight and the local tangent plane at the point of the reflection of the earth. Typically, the SAR image is first formed on the slant plane 102 and then projected to the ground plane 104 with the corresponding resampling as needed.
Additional principles of SAR are presented in McCandless, S. W. and Jackson, C. R., “Principles of Synthetic Aperture Radar”, Chapter 1 of SAR Marine User's Manual, NOAA, 2004.
Other background references include: U.S. patent application Ser. No. 13/173,891; Papson, Scott and Narayanan, Ram, “Modeling of Target Shadows for SAR Image Classification”, 35th Applied Imagery and Pattern Recognition Workshop (AIPR '06); “Expectation Maximization”, docs.opencv.org/modules/ml/doc/expectation_maximization.html; Bradski, Gary and Kaehler, Adrian, Learning OpenCV: Computer Vision with the OpenCV Library, O'Reilly Media, 2008; Pink, Tan Hwee and Ramanathan, U., “Extraction of height information from target shadow for applications in ATC”, Geoscience and Remote Sensing Symposium, 1999, the disclosures of which are incorporated herein in their entireties.